An Investigational Immuno-therapy Study of Nivolumab Monotherapy and Nivolumab in Combination With Ipilimumab in Pediatric Patients With High Grade Primary CNS Malignancies

Inclusion Criteria:

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- Children and adolescents diagnosed with either:

- Diffuse Intrinsic Pontine Glioma (DIPG), in first-line, after completion of standard
radiotherapy

- High Grade Glioma (HGG), recurrent or progressive

- Medulloblastoma, recurrent or progressive

- Ependymoma, recurrent or progressive

- Other high-grade tumors of the central nervous system, recurrent or progressive

- Lansky play score (LPS) for =< 16 years of age or Karnofsky performance scale (KPS)
for > 16 years of age assessed within two weeks of enrollment must be >= 60

- A tumor sample must be available for submission to central laboratory [not required
for DIPG]

Exclusion Criteria:

- Participants with active, known or suspected autoimmune disease

- Participants unable to taper steroids due to ongoing mass effect

- Participants with low-grade gliomas or tumors of unknown malignant potential

- Prior treatment with any drug that targets T cell co-stimulation pathways (such as
checkpoint inhibitors)

Other protocol defined inclusion/exclusion criteria could apply